Extreme pressure lubricant composition



United States Patent No Drawing. Filed Aug. 4, 1958, Ser. No.7 53,129 5Claims. (Cl. 252-475) This invention relates to additives for mineraloil compositions and more particularly to agents which impart extremepressure, increased load carrying capacity and anti-wear properties tolubricants. a

With the advent of higher compression internal combustion engines, muchdifliculty has been experienced in formulating a suitable lubricatingoil composition capable of operating under severe conditions to protecteflectively metal surfaces which come in contact with the oil. his wellknown that the high pressure occurring in certain types of gears andbearings may cause a film of lubricant to rupture with subsequent damageto the machinery. It has been shown that base lubricants such as mineraloil and/or synthetic oil can be improved with regard to their protectiveeffect on rubbing surfaces by the addition of certain substances so thatexcessive wear, scufiing and seizure which normally follow a break inthe film of lubricant can be prevented even under the most unfavorablepressure and speed conditions. Lubricants possessing this highlydesirable property are called extreme pressure lubricants.

Certain classes of compounds can be used to improve specific propertiesof base lubricants. Thus, compounds containing sulfur, chlorine,phosphorus or lead or combinations of these elements may improve theextreme pressure properties of a lubricant. However, the simple presenceof these elements does not guarantee extreme pressure properties andvarious compounds that do have these properties can vary considerably intheir efiectiveness. It is generally believed that the efiectiveness ofan extreme pressure additive is related to its ability to react with andform a protective coating on a bearing surface to be lubricated. To bemost effective, however, the additive must be present in sufficientconcentration at the surfaces to form an adequate film. One method ofrealizing this surface concentration is the use of polar or other typemolecules which have an affinity or attraction for surfaces. Thus, asopposed to the use of a non-polar molecule which will be present in moreor less equal concentration throughout the bulkof the lubricant, a polartype molecule will tend to give a greater concentration of additive atthe metal surface where it is needed.

In a similar manner a strongly polar material which is not an extremepressure additive can interfere With the function of a less polarextreme pressure additive. Thus, a strongly polar non-extreme pressuremolecule may be preferentially deposited from its admixture with anextreme pressure additive and prevent the extreme pressure additive fromforming its protective extreme pressure film.

My invention is directed to a lubricating oil composition containingessentially a major amount of a mineral lubricating base oil, anoil-soluble tetraester of a complex acid and a sulfurized fatty oil. Thecombined tetraestersulfurized fatty oil additives have been found toimprove load-carrying and anti-wear properties of the lubricating oil.The tetraester is formed from carboxylic acid groups preferably of loweraliphatic acids such as acetic, propionic, butyric, and the C and Caliphatic acids and an alcohol, saturated or unsaturated, preferably analiphatic, saturated alcohol having about six carbon atoms or more,preferably about 6 to 20 carbon atoms. In general the acid has thefollowing molecular structure:

HOOC-R R-OOOH NR'-N HOOC-R R-COOH where R is a divalent hydrocarbonradical of say 1 to 5 carbon atoms and R is a divalent hydrocarbonradical preferably aliphatic, of 2 to 6 carbon atoms. The preferred acidfor my invention is ethylene'diamine tetraacetic acid and has thefollowing molecular structure:

nooo-om urn-coon N-CHa-CHr-N Hooo-c our-coon The ethylene diaminetetraacetic acid used in forming the reaction products is an eflicientchelating agent; that is, a chemical which complexes polyvalent metallicions with a multi-n'ng structure that inactivates the metal. Thisproperty has been used in a variety of applications.

The preferred alcohols of my invention are saturated alcohols havingfrom about 6 to 20, advantageously 6 to 12, carbon atoms such as octylalcohol, decyl alcohol, tetradecyl alcohol, hexadecyl alcohol, and thelike. These aliphatic alcohols are preferred, but it Will be understoodthat unsaturated, and aromatic alcohols may be substituted in whole orin part in formating the ester reaction product.

In making the ester the appropriate acid and methanol are mixed, and thesolution is refluxed and heated for the necessary period of time toobtain esterification. The time of. refluxing is related to theparticular constituents employed and is not considered critical. Theperiod of time will generally range from about 2 to 14 hours. Afterrefluxing is completed excess alcohol is distilled off. Then asufficie'nt quantity of a low molecular weight alcohol such asisobutanol along with a catalyst such as octylene glycol titanate isadded to facilitate transesterification. The constituents are heated forap proximately 5 to 8 hours at a temperature of about 120 to 140 C. Theproduct thus obtained is added to a higher molecular weight saturatedalcohol and a solvent such as xylene and a catalyst such as octyleneglycol titanate is added to facilitate ester interchange. The reactionis now maintained at a temperature from about to C. for a period of fromabout 5 to lo hours. The solvent is then removed by distillation.

The mineral oil base stock used in the present iuveution is oflubricating viscosity and can be for instance a solvent extracted orsolvent refined oil obtained in accordance with conventional methods ofsolvent refining lubricating oils. Generally, lubricating oils haveviscosities from about 20 to 250 SUS at 210 F. The base oil may bederived from paraflinic, naphthenic, asphaltic or mixed base crudes, andif desired, a blend of solvent-treated Mid-Continent neutrals andMid-Continent bright stocks may be employed. A particularly suitablebase oil used in the preparation of the compositions describedhereinafter is a solvent treated Mid-Continent neutral having aviscosity index of about 95.

The amount of tetraester added to the mineral oil will vary dependingupon the particular characteristics of lubricating oil utilized althoughsuflicient ester is present to give the desired effect. In general fromabout 0.1 percent of the ester by weight to about 10 percent of thefinal composition by weight is preferred in my lubricating oilcomposition. Although my additive has been described as the tetraesterit may contain portions of less esterified materials such as diandtri-esters.

The sulfurized fatty oils preferred for my invention are for instance,sulfurized sperm oil, sulfurized rapeseed oil, sulfurized cotton seedoil and sulfurized palm oil. These oils in general are essentiallyesters, e.g. glycerides, of

acids of 12 to 18 carbon atoms. A particularly effective EXAMPLES 73grams of ethylene diamine tetraacetic acid are added to 320 grams ofmethyl alcohol and refluxed with stirring for a period of about 3 hours.grams of concentrated HCl is then added and the mixture is refluxed forabout 8 hours and then the reaction product is recovered and the excessalcohol is distilled oil. The light amber, viscous product is found tobe insoluble in mineral oil, di-(2- ethylhexyl) -sebacate, toluene and2-ethylhexanol, but soluble in isobutanol. 225 grams of isobutanol and 1gram of octylene glycol titanate are added to the above product tofacilitate ester interchange. The reaction is maintained atapproximately 130 C. for a period of about 6 hours. 260 gramsofethylhexanol are added and the reaction is maintained at about 150 C.for five hours. This is accomplished by gradually recovering the refluxas distillate during the above period. The product is called product Aand analyzed as containing 3.87% nitrogen.

The following tests were conducted on the indicated blendedcompositions:

Shell 4-ball wear test Mean Hertz load SAE load test Timken L-20 testThese tests have been fully described in literature on the subject ofanti-wear and extreme pressure testing. Thus, I will not attempt to gointo any detail concerning the procedure of each. The possible exceptionto the above is the Timken L-20 test which is I'llIl using the Timkenmachine described in CRC L18545. The test block is continuously movedback and forth beneath the test cup in a direction paralleling the levelarm for a distance for about 0.13 inch at an approximate rate of about 4times per minute. Conditions for load, speed, time and temperature maybe varied and are noted for a given test.

Table I Composition 1 2 3 4 Base Oil, Wt. Percent 98 95 93 Product A,Wt. Percent 2.0 2.0 Sulfurized Sperm Oil (12% S), Wt. 5.0 5.0

Percent. Tests:

Shell et Ball Wear Test, Scar 0.687;... 0. 500 0. 445 0. 400

Diarn., mm. (7 Kg., 2 hrs, (3., 640 r.p.m.). Mean Hertz Load 13.7 20.33.7 37. 6 SAE at 300 r.p.rn.-, lbs 84 136 333 Timken L-20 test, Totalwear,

Fails at (100 lbs., 200 .F., 200 Start of S9. 5 32.2 15.3

r.p.m., 16 hrs.). Test. lbs., 200 F., .200

r.p.n1., 16 hrs.).

1 Solvent refined Mid-Continent neutral oil, viscosity 33 SUS at 100 F.

The above data clearly demonstrate the improved antiwear properties,increased load carrying capacity and extreme pressure properties ofmycompositions.

I claim:

1. A lubricating oil composition consisting essentially of a minerallubricating base oil, and about 0.1 to 10% of an oil-soluble tetraesterof an alcohol having about 6 to'20 carbon atoms and a carboxylic acidhaving the following molecular structure:

HOO CR R-COOH wherein R is a divalent hydrocarbon radical of 1 to 5carbon atoms and R is a divalent hydrocarbon radical of 2 to 6 carbonatoms, and about 1 to 15 percent of a sulfurized fatty oil.

2. The lubricating oil composition of claim 1 wherein the sulfurizedfatty oils are of acids of 12 to 18 carbon atoms and contain about 5 to15% combined sulfur.

3. The lubricating oil composition of claim 1 in which the acid isethylene diamine tetraacetic acid.

4. The lubricating oil composition of claim 3 in which the sulfurizedfatty oil is sulfurized sperm oil containing about 5 to 15 combinedsulfur.

5. A lubricating oil composition consisting essentially of a minerallubricating base oil and about 0.1 to 10% of the final composition of anoil-soluble tetraester of an alcohol of 6 to 12 carbon atoms and acarboxylic acid having the following molecular structure:-

and about 3 to 8% of sulfurized sperm oil containing about 5 to 15%combined sulfur.

References Cited in the file of this patent UNITED STATES PATENTS2,162,398 Haas June 13, 1939 2,203,507 Roehner et al. June 4, 19402,680,094 Bartlett et al. June 1, 1954

1. A LUBRICATING OIL COMPOSITION CONSISTING ESSENTIALLY OF A MINERALLUBRICATING BASE OIL, AND ABOUT 0.1 TO 10% OF AN OIL-SOLUBLE TETRAESTEROF AN ALCOHOL HAVING ABOUT 6 TO 20 CARBON ATOMS AND A CRBOXYLIC ACIDHAVING THE FOLLOWING MOLECULAR STRUCTURE: